1. Technical Field
The present invention relates to a physical quantity detection device, a physical quantity detector, and an electronic apparatus.
2. Related Art
A physical quantity detection device (such as an acceleration sensor) which includes a physical quantity detection element such as an oscillator is known. This type of physical quantity detection device is so designed as to detect a force (acceleration) applied to the physical quantity detection device based on a change of the resonance frequency of the physical quantity detection element produced by a force acting in the direction of the detection axis.
In JP-T-4-505509, there is disclosed a sensor which has a double-ended crystal tuning fork converter (physical quantity detection element) both ends of which are fixed to a support structure containing a base assembly, a deflection, and a guaranteed mass.
According to the technology disclosed in JP-T-4-505509, however, a stress produced between plural fixing portions of the support structure when the support structure is fixed to a package, for example, due to the difference in the coefficient of linear expansion between the support structure and the package, may reach the physical quantity detection element via the support structure, and change the resonance frequency of the physical quantity detection element. In this case, the detection sensitivity of the physical quantity detection device deteriorates.
For avoiding transmission of this stress, a technology disclosed in U.S. Pat. No. 5,331,854 provides beam-shaped bended portions on a support structure supporting a physical quantity detection element, between which bended portions a guaranteed mass is sandwiched, so as to reduce the stress by using the bended portions.
According to the technology shown in U.S. Pat. No. 5,331,854, the bended portions are provided such that the guaranteed mass is sandwiched therebetween. In this case, the distance between the bended portions, that is, the distance between the plural fixing portions of the support structure fixed to the package is difficult to be reduced to a length equal to or shorter than the width of the guaranteed mass or the support structure (a length equal to or shorter than the distance between the roots of the two bended portions at the junction with the support structure). Thus, when the bended portions are fixed to the package, for example, the stress produced on the support structure by the difference in the coefficient of linear expansion between the support structure and the package may increase in accordance with the distance between the plural bended portions (fixing portions). In this case, the raised stress may reach the physical quantity detection element.